I'm working through this issue now...
I have the same symptoms as above.
Started with ABS light solid and dead speedo.
Then Rev counter would fall along with service and battery lights coming on.
Car would drive ok although I think its in limp mode.
Don't think it has anything to do with battery (which is only 6months old) or alternator as I've piggyback the power off another vehicle using decent jump leads. Battery and alternator read fine anyway.
I've found that if I remove Fuse
#1 in the engine bay, which is the 20A ABS, the car works fine.
No issues with the rev counter and lights flickering.
Albeit since the ABS is disabled you don't get a working speedo, odometer and the ABS light stays lit.
Apart from that the car works fine and drives normally.
I've checked all the ABS sensor connections and all were solid with no debris inside.
I'm waiting on a Haynes manual to be delivered to start investigating a possible ABS pump or wiring issue.